This invention relates to fabrication of semiconductor junctions and provides methods for fabricating semiconductor junctions on a substrate. The invention relates also to corresponding semiconductor structures obtainable by such methods.
It is known that semiconductor structures can be formed by patterning trenches of the desired shape on a substrate and then depositing semiconductor material to fill the trenches. A fundamental problem with the patterned-trench technique is that defects tend to occur in the resulting crystal structure of the semiconductor. One technique to restrict these defects, known as aspect ratio trapping (ART), involves controlling the aspect ratio of a trench defined between sidewalls of a mask such that dislocations in the semiconductor structure formed in the trench tend to terminate at the mask sidewalls. Defects are then inhibited in an upper region of the semiconductor structure above the dislocations.
Defects have also been reduced in semiconductor structures using the technique of confined epitaxial layer overgrowth (ELO). With this technique, planar semiconductor structures have been grown laterally (i.e. generally parallel to the plane of the substrate) from seeds in the form of elongate stripes of monocrystalline semiconductor material. Selective epitaxial growth proceeds laterally from the seed stripes in tunnel areas defined between upper and lower confining surfaces.
An improved technique for fabrication of semiconductor junctions would be highly desirable.